Metathesis is one of a crucial reaction for the petrochemicals industry, especially the cross-metathesis of ethene and n-butene which is an economical mean for selectively producing highly demanded propene. Factors affecting feasibility of the process include conversion, selectivity, energy consumption, and reaction cycle time.
Attempts have been made in improving overall efficiency of olefin metathesis process. Several approaches were employed. For example, U.S. Pat. No. 4,575,575 discloses a metathesis reaction between ethene and 2-butene carrying out in the presence of a catalyst of silica-supported tungsten oxide in combination with a magnesium oxide co-catalyst.
U.S. Pat. No. 3,658,929 discloses processes for olefins conversion, including olefins metathesis, wherein the olefins feeds are pretreated by contacting with magnesium oxide prior to the conversion.
U.S. Pat. No. 5,120,894 also discloses a process for olefin conversion wherein the reaction zone is a catalyst bed configured so that the upstream end of the bed is magnesium oxide and the downstream end of the bed is a mixture of magnesium oxide and tungsten oxide on silica catalyst.
In these disclosures magnesium oxide was used to perform double bond isomerization of the olefin feed, such as isomerization of 1-butene to 2-butene, in order to achieve higher olefin conversion rate. However, magnesium oxide normally sinters at high temperature and therefore its performance usually drops significantly after regeneration.
US 20100145126 A1 discloses a process of producing olefins through a metathesis reaction, wherein the catalytic reactivity is improved by allowing co-existence of hydrogen gas. However, side reactions can occur between hydrogen and olefin feed or product and therefore product yield is reduced.
US 2008/0194903 A1 discloses a method for purifying a starting product comprising contacting a feed stream with an adsorbent which has been activated comprising at least 3% by weight of aluminum oxide to remove one or more impurities from the feed stream. The adsorbent activation is conducted at high temperature and therefore high energy is required.
Another factor that could play an important role on metathesis catalyst efficiency is in the catalyst shaping process. Typically, heterogeneous catalysts, including metathesis catalyst, are initially prepared in powder form. They needed to be shaped into an appropriate structure, for example, sphere, tablet, or extrudate, prior to be used in an industrial process.
An appropriate structure provides good mechanical strength, easier handling, and prevent high process pressure drop. A catalyst binder is usually added to the catalyst composition during catalyst shaping process for binding powder materials together. Choices of binder can significantly affect physical properties and also catalytic performance of the final catalyst. If a proper hinder that does not adversely affect catalyst efficiency can't be identified or obtained, a suitable solution needed to be figured out in order to resume catalyst efficiency during its utilization in the process.